i would agree with most of the comments about what to do with kids. and having been one my self any time my parents had company over sleep was the last thing on my mind. Even knowing the fact that all they did was play card with the neighbors. of course i was playing my self but that is a another matter all together. so i would suggest that you work on finding a regular nite that you could get your son to spend out of the house.
i know you said the what happened was the first time i am sure you hope it will not be the last. so the thing is to plan. if by chance you might find a friend or relative that you might be able to seed you son over to spend the nite at the last minute would be ideal or at the very least maybe you could trade with a family that would need to get their kids out of the house for an adult nite (could be cards or any thing) then they could help you out also. having kids is great but that doesn't mean i like have them around 24/7.